The Nigerian Communications Commission (NCC) has reduced the fine it fined South African telecoms MTN over unregistered SIM cards, the company has said.

The NCC has reduced the fine to $3.4 billion down from an earlier $5.2 billion, after negotiations.

MTN was fined in October after it missed a deadline to disconnect 5.1 million unregistered SIM cards.

The reduced fine has to be paid by December 31.

Africa’s largest mobile phone operator said in a statement is was “carefully considering” the revised fine by the NCC.

It said executive chairman Phuthuma Nhleko “will immediately and urgently re-engage with the Nigerian authorities before responding formally…to ensure the best outcome for the company, its stakeholders and the Nigerian authorities.”

“All factors having a bearing on the situation will be thoroughly and carefully considered before the company arrives at a final decision.”

The fine resulted in the resignation of the group’s chief executive Sifiso Dabengwa in November, after news of the penalty sent the firm’s share price plummeting.

Dabengwa has been replaced by Phuthuma Nhleko, the firm’s former chief executive who will hold the position for six months.

Meantime two senior executives at the company’s operation in Nigeria have stepped down, the firm announced.

MTN Nigeria’s CEO Michael Ikpoki and the head of regulatory and corporate affairs, Akinwale Goodluck “have tendered their resignations with immediate effect,” MTN said in a statement.

Nigeria, Africa’s most populous country, is MTN group’s largest market where it had over 62.8 million subscribers by the second quarter of this year.

The NCC said registration of subscribers was made mandatory to ensure proper identification of users with their biometric data and in line with international best practice.